Electrostatic image-forming apparatus and process

ABSTRACT

An electrostatic image-forming process using a plate comprising a substrate, a photoconductive layer and an insulative layer includes the steps of placing an insulative recording member in contact with the insulative layer, the recording member either being previously charged or being charged while in position on the insulative layer, and applying a voltage to the plate and simultaneously irradiating the photoconductive layer with a pattern of image radiation. Apparatus is also disclosed for use in such process and particularly for conversion of electron beams to provide the pattern of image radiation.

United States Patent Inoue et al.

ELECTROSTATIC IMAGE-FORMING APPARATUS AND PROCESS Eilchl lnoue; KelzoYamqii; l-liroshi Tanaka; Takashl Salto, all of Tokyo, Japan Inventors:

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data [15] 3,653,064 1 51 Mar. 28, 1972Primary Examiner-Howard W. Britton Attorney-Watson, Leavenworth andKelton [57] ABSTRACT Feb. 25, 1968 Japan ..43/11875 Feb 27, 1968 Japan t43/12739 An electrostatlc 1mage-f0rm1ng process usmg a plate compns-Feb. 27, 1968 Japan ..43/12740 ing a Substrate, a Photoconductive layerand an insulative I layer includes the steps of placing an insulativerecording us. (:1. ..346/74 ES, 96/1 PC,346/74 EB, member in Contactwith the insulative layer, the recording 34 /74 p member either beingpreviously charged or being charged 1111. C1 ..G03g 5/02, 603g 13/00,003 15/00 while in position on the ihsulative layer, and pp y g avoltage Field of Search ....346/74 ES, 74 ES X, 74 EB, t0 the plate nsim l neously irradiating the photoconduc- 346/74 P; IOI/DIG. 13;.96/1R, 1 PC, 1 C; 250/495 tive layer with a pattern of image radiation.Apparatus is also C, 49.5 ZC disclosed for use in such process andparticularly for conversion of electron beams to provide the pattern ofimage radiation.

17 Claims, 37 Drawing Figures 1 8' J33 3 B W- 2 PATENTEMAR28|9123,653,064

sum 3 OF 8 FIG.60

PATENTEUMAR28 I972 3,653,064

SHEET 5 BF 8 FIG. '9

CLEANER c I, C

DEVELOPING X PROCESSOR 13 SYNC.

SEPARATOR PATENTEQMAR 28 I972 SHEET 8 [IF 8 FIG.12

FIG.II

FIG.I4

FIG. 13

PATENTEDmze m2 SHEET 8 OF 8 FIG.2O

' projecting the light images upon a xerographic plate,

ELECTROSTATIC IMAGE-FORMING APPARATUS AND PROCESS image-formingprocesses.

One known method for electrostatically recording informaconductive pinsbedded in a matrix. Information signals one another are emare convertedinto electron beams by the cathode ray tube and the electron the imagesare distorted. Thus, it is difficult to form high contrast electrostaticpatterns.

- Another method is disclosed in U.S. Pat. No. 3,132,206 issued to P. F.King. According to this method, the information images are used as lightimages for the image-forming in accordance with the Carlson process,i.e., by

thereby forming electrostatic patterns on the photoconductive sameresults, process.

the third step of applying uniform radiation thereto.

Alternatively, another process of the present invention includes thefirst step of applying a first voltage to the face plate of a cathoderay tube incorporating the above-described without the charge-retainingrecording member, are maintained in the form of a lamination.

According to the ing a relatively low resistance may be used, therebyproviding a highly sensitive photoconductive member.

According to the present invention, images displayed on the phosphorscreen by the electron beams of a cathode ray tube cathode ray tube,thereby forming an electrostatic image in the charge-retaining member.Therefore, light image loss is less, and generation of electron beamsand radiation and the formation of electrostatic images can be effectedwith high efficiency.

As described above, in the processes of the present invention, theelectrostatic images are formed in the charge-retaining insulative layerof the photoconductive member so that application of the first voltageand processing following formation of the electrostatic image can beeffected even in ambient light. 1

Furthermore, when said insulative layer is made of a material which isnon-transmissive to radiation applied with the second voltage and towhich the photoconductive layer is sensitive, the entire process can becarried out in ambient light.

The electrostatic charge images formed by the processes of the presentinvention can be rendered permanently visible by applying toner to colorthe image, by the frost method or by any suitable method for recording.Alternatively, the electrostatic image can be transferred to a copyingor recording material.

One of the objects of the present invention is to provide a novelelectrostatic recording process.

Another object of the present invention is to provide a cathode ray tubeincorporating a multilayer face plate adapted to convert electron beamsignals into radiation images or patterns.

A further object of the present invention is to provide an improvedrecording tube adapted to provide electrostatic patterns upon the faceplate thereof.

Another object of the present invention is to provide an improvedrecording tube having means for uniformly illuminating the face platethereof with radiation.

A still further object of the present invention is to provide recordingprocesses for recording electrostatic patterns by conversion of electronbeam signals controlled by information signals.

A further object of the present invention is to provide a recordingprocess comprising the step of applying voltage to a face plateincorporating a photoconductive layer and simultaneously applyingelectron beams thereto, thereby efiiciently recording the electron beamsignals as electrostatic patterns upon a charge-retaining member.

A still further object of the present invention is to provide arecording process for forming high contrast electrostatic images upon aphotoconductive member having a charge retaining insulative layer.

A still further object of the present invention is to provide anelectrostatic recording process which permits the use of highlysensitive photoconductive materials.

Another object of the present invention is to provide a recordingprocess for forming high contrast electrostatic images even in ambientlight.

Another object of the present invention is to provide an improvedprocess for permanently recording electrostatic images corresponding toelectron beam signals.

The above and other objects, advantages and features of the presentinvention will become more apparent from the following description takenin conjunction with the accompanying drawings.

FIG. 1 illustrates the structure of a photoconductive member used in thepresent invention.

FIGS. 1a 1c illustrate a process for forming electrostatic images usingthe photoconductive member shown in FIG. 1.

FIG. 2 is a diagram a surface potential attained in the process of FIGS.la- 1c.

FIG. 3a illustrates another photosensitive member structure according tothe present invention and FIGS. 31 3c illustrate a process for formingan electrostatic image using the photoconductive member shown in FIG.3a.

FIG. 4 is a diagram of surface potential attained in the process ofFIGS. 3a 30.

FIGS. 5a 5f illustrate structures of photoconductive members for use inprocesses of the present invention.

FIGS. 6a 6g illustrate structures of face plates for cathode ray tubesaccording to the present invention.

FIGS. 7 l6, l8, l9 and 21 illustrate further processes of the presentinvention.

FIGS. 17 and 20 illustrate other embodiments of face plates for cathoderay tubes according to the present invention.

Referring now particularly to FIG. 1, which illustrates the fundamentalstructure of a photoconductive member used in the process of the presentinvention for converting radiation into an electrostatic image,photoconductive layer 2 is formed upon substrate 1 by a coater, wheeler,etc. or by sputtering, vacuum deposition, etc. and, if required, a smallquantity of a binder such as resin or the like may be added to thematerial forming photoconductive layer 2. Insulative layer 3 is formedupon photoconductive layer 2. The photoconductive member must haveessentially these three layers, i.e., substrate 1, photoconductive layer2 and insulative layer 3 for electrostatic image-forming.

Substrate 1 may be made of an insulative or electrically conductivematerial or a lamination composed of photoconductive and insulativelayers. Such conductive materials include metal conductors such asaluminum, copper and the like, humid paper, Nesa coating, glass and soon. Suitable insulative materials are selected from the same materialsused for insulative layer 3 which will be described in more detailhereinafter, but are not limited thereto and may be selected from a widerange of insulative materials known in the art.

Materials for photoconductive layer 2 include cadmium sulfide, cadmiumselenide, crystal and amorphous selenium, zinc oxide, zinc sulfide,titanium dioxide, selenium telluride, lead oxide, sulfur and otherchalcogenide compounds, inorganic photoconductors and organicphotoconductors such as anthracenes, carbazoles and so on. The materialsmay be coated upon the substrate, or a mixture of the above materialswith or without a binding agent may be used or they may be formed intolaminations consisting of more than two layers. Among theabove-described photoconductive materials, the materials best suited foruse in the present invention are CdS, CdSe, SeTe, and so on, and withuse thereof sensitivity can be elevated to higher than ASA 100. Thepresent invention can employ photoconductive materials having relativelylow resistance values, which materials have not been used inconventional processes in which electric charges must be maintained inthe photoconductive layer. Such materials can be used in the presentinvention since charge maintaining capability is imparted to thephotoconductive layer by the insulative layer superposed thereupon.

The characteristics required for insulative materials are (a)sufficiently high resistivity to retain electrostatic charge and (b)resistance to abrasion, and any material satisfying these conditions maybe used as the insulative layer in the present invention. When theradiation image is applied to photoconductive layer 2 through theinsulative layer, the insulative material must be transparent toactivating radiation. On the other hand, when the substrate is made of amaterial, for example, Nesa glass or the like which permits thetransmission of the activating radiation therethrough and when theradiation image is applied to the photoconductive layer through thissubstrate, the insulative layer need not be transparent. For example, afilm or coating of fluorine resin, polycarbonate resin, polyethyleneresin, cellulose acetate resin, polyester resin and so on may be used.Furthermore, glass made of A1 0 SiO etc., ceramic, inorganic compoundthin layers and so on, which are or are not transparent, may be used.

The processes for forming electrostatic images upon insulative layer 3of the photoconductive member will now be described. First a processwill be described wherein substrate 1 is made of conductive material andwherein application of a second voltage by AC corona discharge isperformed simultaneously with emission of radiation. As shown in FIG.1a, the surface of insulative layer 3 of photoconductive plate A iselectrically charged, for example in positive polarity, by corona device5 connected to high voltage DC source 4. In this case, it is presumedthat negative charges are injected from the conductive substrate sideand are bound at the interface between photoconductive layer 2 andinsulative layer 3 or within photoconductive layer 2 adjacent toinsulative layer 3. In this process, the surface potential of insulativelayer 3 in creases as charging time. elapses as illustrated in FIG. 2 bycurve V It is of course possible to effect the above-described chargingby using an electrode instead of corona discharge. It should be notedthat this charging step can be performed in ambient light.

When photoconductive layer 2 has n-type semiconductivity the insulativelayer is preferably charged positively. When photoconductive layer 2 hasp-type semiconductivity, the insulative layer is preferably chargednegatively.

Then as shown in FIG. 1b, a radiation image (a light image will be usedherein for the sake of convenience of description) is projected uponinsulative layer 3 while simultaneously AC corona discharge is appliedthereto from charging device 8 connected to high voltage AC source 9.When the light image is projected through insulative layer 3 as shown inFIG. 1b, the upper end of charging device 8 must be optically open.After projection of the light image and charging by AC corona discharge,the positive charges provided by the first charging are all or almostall discharged by the AC corona discharge where these positive chargesare located at portions of the surface of insulative layer 3 which wereilluminated by the light image. Such discharge is dependent upon ACcorona discharge time and intensity. In this case, the resistance ofphotoconductive layer 2 is reduced where illuminated by the light imageso that layer 2 becomes conductive. Consequently, the negative chargesbound at the interface between photoconductive layer 2 and insulativelayer 3 or within photoconductive layer 2 adjacent to insulative layer 3become free and are discharged as the surface charges upon insulativelayer 3 are discharged. Almost all of these negative charges aredischarged into conductive substrate 1. Therefore, the surface potentialof the image-illuminated portions of insulative layer 3 is reduced as ACcorona discharge time elapses as shown in FIG. 2 by curve V,

The positive charges at portions of insulative layer not illuminated bythe light image are also discharged by the AC corona discharge, but suchdischarge is less than that described above for charges at illuminatedportions. The negative charges bound in image-unilluminated portions ofthe photoconductive member are not discharged by AC corona dischargebecause of the high resistance of such imageunilluminated portions ofphotoconductive layer 2. Therefore, the positive charges in thecorresponding portions of insulative layer 3 are maintained or remainalmost unchanged. In imageunilluminated portions of insulative layer 3many more positive charges are retained than in image-illuminatedportions thereof. However, a large number of negative charges stillremain bound in photoconductive layer 2, so that the electrical fielddue to the surface potential of insulative layer 3 is influenced ratherstrongly by the negative charges bound in photoconductive layer 2,whereby the external field due to the surface potential is extremelyslight or negligible. The surface potential in the image-unilluminatedportions is less than the surface potential in the image-illuminatedportions as illustrated in FIG. 2 by a curve V Thus, surface potentialdifferences (V V are provided upon the surface of insulative layer 3 inaccordance with the light image pattern, thereby forming anelectrostatic image of the light image. These surface potentialdifferences (V V vary as shown in FIG. 2 when the light image isprojected while simultaneously applying AC corona discharge, so that theimage projection and AC corona discharge time must be selected suitablydepending upon the sensitivity of the photoconductive plate, ACdischarge conditions and so on in order to obtain large surfacepotential differences.

Thereafter, the surface of insulative layer 3 upon which suchelectrostatic image has been formed is exposed to radiation 10 as shownin FIG. 1c. In this case, the image-illuminated portions ofphotoconductive layer 2 remain substantially unchanged, so that thepositive charges upon the surface of insulative layer 3 also remainsubstantially unchanged, thereby maintaining the surface potential asshown in FIG. 2 by the curve V On the other hand, theimage-unilluminated portions of photoconductor layer 2 which havemaintained high resistance since they have not been exposed are nowexposed to activating radiation in this step and the resistance thereofis rapidly reduced and they become conductive. Consequently, thenegative charges bound therein are almost all dischargedinto'electrically conductive substrate 1 and only a very small portionof the charges are bound by the field of the positive charges upon thesurface of insulative layer 3. Thus, positive surface charges, that is,charges having the same polarity as the first or initial chargesprovided upon the surface of insulative layer 3, which charges provide afield acting strongly upon negative charges bound in photoconductivelayer 2 in the previous step, now act to provide an external field. Thesurface potential of insulative layer 3 is thereby rapidly increasedupon exposure of the whole surface of the insulative layer 3 toactivating radiation as illustrated in FIG. 2 by curve V As describedabove, when the whole surface of insulative layer 3 is exposed toactivating radiation, the surface potentials V and V become V and Vrespectively, so that the surface potential of the image-unilluminatedportions becomes higher than that of the image-illuminated portions.That is, the respective surface potentials are reversed, and thedifference therebetween increases.

According to one process of the present invention, the surface of theinsulative layer is charged in maintaining equilibrium with chargesinduced in the photoconductive layer underlying the insulative layer,and a surface differential is provided upon the surface of theinsulative layer by interaction of the charges upon the insulative layerand those in the photoconductive layer, thereby forming an electrostaticimage in accordance with the light-dark pattern of the original image.Therefore, as compared with conventional electrophoto graphic methods inwhich electrostatic images are formed upon the surface of thephotoconductive layer, the electrostatic image formed by the presentinvention has a stronger external field and a large surface potential,thus increasing sensitivity.

In the present invention, a fluorescent image formed upon the face plateof a cathode ray tube is used as the radiation image and use of theprocess of the present invention is very advantageous in formingelectrostatic patterns from such low intensity fluorescent images, inproviding rapid development and in providing high sensitivity.

In FIG. 3, another embodiment of the present invention is shown whereinthe voltage application which is performed simultaneously with theprojection of the light image is provided by DC corona discharge havingthe same polarity with that of the first charging. Substrate l ofphotoconductive plate B is made of a radiation transmissive materialsuch as Nesa glass or the like having a Nesa coating 11 thereon and thelight image is projected upon the photoconductive layer thereof throughthe substrate. Such process is substantially similar to the processdescribed above with reference to FIG. 1.

The first step is, as in the case of FIG. 1a, to positively charge thesurface of insulative layer 3 (FIG. 3a). In the second step, as shown inFIG. 312, light image 12 is projected through substrate 12 whiledischarging device 8 supplied with a high negative potential issimultaneously moved across the surface of insulative layer 3. Wheninsulative layer 3 is made of a material which is transmissive to thelight image, the upper end of the shield plate of discharging device 8is optically closed so as to prevent radiation, except that from thesubstrate side, from impinging upon the surface of insulative layer 3.On the other hand, when the insulative material is non-transmissive tothe light image, the provision is not necessary and furthermore thisprocess may be carried out in ambient light.

Portion L of photoconductive layer 2 is illuminated by the light imagein the second step and reduces its resistance to the charges boundtherein in the first charging step. Furthermore,

the positive charges upon the corresponding image-illuminated portion ofthe surface of insulative layer 3 are discharged by the negative coronadischarge applied thereto simultaneously with the projection of thelight image and such portion is then negatively charged. Concurrently,positive charges are induced at the interface between the insulative andphotoconductive layers or within the photoconductive layer adjacentthereto.

On the other hand, in image-unilluminated portion D, the positivecharges applied to the surface of insulative layer 3 by the firstcharging step are partially or completely neutralized by the negativecharges applied thereto in the second step. In this case, the degree towhich such portion of the insulative layer surface is negatively chargedis less than in the case of portion L as described above. This meansthat the external field due to the persistently bound carriers has astrong influence.

Next, the whole surface of insulative layer 3 upon which anelectrostatic charge pattern was formed in the second step is exposed toactivating radiation 13. In this case, in portion L the condition ofphotosensitive plate A remains substantially unchanged so that thesurface potential of insulative layer 3 remains substantially unchanged.On the other hand, at portion D which has a high resistance, theresistance is rapidly reduced as this portion is exposed to activatingradiation in this third step and portion D becomes electricallyconductive. Therefore, the charges bound internally in the previous stepare discharged into the electrically conductive substrate. Concurrently,positive charges are induced in photoconductive layer 2 by the negativecharges upon the surface of insulative layer 3. Consequently, thesurface potential of the surface of insulative layer 3 is rapidlyreduced so that the field due to the negative charges on insulativelayer 3 acts strongly upon the positive charges induced inphotoconductive layer 2 while the external field due to the surfacecharges becomes negligible.

On the other hand, when the external field due to the internally boundcharges is very strong, the charges imparted in the first step may notbe completely neutralized even after the second step. In this case, theexternal fields are superposed and provide a net field of zero, andsince the bound charge field is released upon illumination of activatingradiation over the whole surface of the insulative layer, theelectrostatic contrast of positive and negative charge combination isobtained with resultant high contrast. The surface potentials of theelectrostatic pattern formed upon photoconductive plate B after thethird step are shown in FIG. 4, the reference characters of which havethe same meaning as in FIG. 2.

So far the process of the present invention has been described withparticular reference to FIGS. 1 through 3 with use of theabove-discussed fundamental photoconductive plates. The photoconductiveplates whose structures are shown in FIG. 5 may be used in applicationsof processes of the present invention based upon the same conceptsdiscussed heretofore.

The photoconductive plate shown in FIG. 5a is similar to that shown inFIG. 1 with the exception that between photoconductive layer 2 andelectrically conductive substrate 1 is interposed insulative layer 14.In other words, the substrate is composed of electrically conductivelayer 1 and insulative layer 14 laminated thereupon. Insulative layer 14serves as a blocking layer upon charging to block injection of chargesfrom the electrode. During the electrostatic image-forming process,charges active in photoconductive layer 2 of the photoconductive plateshown in FIG. 5a are free carriers existing in photoconductive layer 2and photocarriers induced upon illumination thereof by radiation.Therefore, when the first charging step is conducted with accompanyinguniform illuminating radiation, sufficient binding of charges isprovided adjacent both of photoconductive layer 2 and insulative layer3.

The photoconductive plate shown in FIG. 5b is similar to that shown inFIG. 5a with the exception that the electrically conductive substrate 1is removed therefrom so that insulative layer 14 constitutes the onlysubstrate of this photoconductive plate. When this photoconductive plateis used, chargings and illuminating radiation are carried out inconjunction with an additional electrode, which will be described inmore detail hereinafter. The photoconductive plate shown in FIG. 50 issimilar to that shown in FIG. 1 with the exception that substrate 1 isremoved therefrom. This plate may be used in a similar process as in thecase of the plate shown in FIG. 5b. The photoconductive plate shown inFIG. Sr! is similar to that shown in FIG. 1 with the exception thatinsulative layer 3 is removed therefrom. This plate may be used in aprocess wherein, after the first charging of the photoconductive plate,an insulative layer (not shown) is overlaid thereupon or an insulativefilm (not shown), which has been previously charged, is overlaidthereupon. The photoconductive plate shown in FIG. Se is also similar tothat shown in FIG. 5a with the exception that insulative layer 3 isremoved therefrom. This plate may be used in the same manner as in thecase of the photoconductive plate shown in FIG. 5d. The photoconductiveplate shown in FIG. 5f is similar to that shown in FIG. 5e with theexception that substrate 1 is removed therefrom. This plate may be usedin a process wherein the first charging step is carried out as in thecase of the photoconductive plate shown in FIG. 5d and then the secondstep is carried out as in the case of the photoconductive plate shown inFIG. 5b.

A special face plate for a cathode ray tube will now be described withreference to FIG. 6. The face plate, as shown in FIG. 6a, comprises atleast phosphor layer 15 adapted to illuminate upon bombardment thereofby electron beams, vacuum envelope 16 transmissive to light and made ofglass or the like, and light-transmissive thin layer electrode 17. Thisface plate may be suitably utilized in combination with one of thephotoconductive plates shown in FIG. 5 in one of the processes whichwill be described in more detail hereinafter. In the face plate shown inFIG. 6b fiber optics are applied to the face plate of the cathode raytube envelope instead of glass layer 16 of the face plate shown in FIG.6a. This arrangement prevents diffraction within the glass of the imageformed at phosphor screen or layer 15. As shown in FIG. 6b, thinconductive layer 19 may be interposed between phosphor screen or layer15 and glass envelope 18 to constitute the anode of the cathode raytube. Alternatively, a metal backing (not shown) formed from thin layeraluminum may be coated upon the inner surface of phosphor screen 15 ifneeds demand.

The above-described fiber optics, anode and metal backing will not bediscussed specifically in the following description of the face platesshown in FIGS. 60 through 6g, but it should be understood that same maybe incorporated in these face plates as needs demand.

In the face plate shown in FIG. 60 thin insulative layer 20 similar tolayer 14 in FIG. 5a is disposed upon transparent electrode 17 of theface plate of FIG. 6a. In this case, this thin insulating layer must betransmissive to the radiation employed. This face plate cooperates withone of the photoconductive plates shown in FIG. 5b, FIG. 56 and FIG. 5fin the second step of the process.

In the face plate shown in FIG. 6d photoconductive layer 21 is disposedupon insulative layer 20 of the face plate shown in FIG. 60. This platemay be used in forming electrostatic patterns upon a recordinginsulative film overlaid upon this face plate.

In the face plate shown in FIG. 6e insulative layer 22 is disposed uponthe face plate shown in FIG. 6d. Such additional insulative layer 22itself can serve as a medium for generating a phosphor or luminescentimage and for converting this image into an electrostatic image as willbe described in more detail hereinafter.

Face plates shown in FIG. 6f and FIG. 6g are respectively similar tothose shown in FIG. 6d and FIG. 6e with the exception that blockinginsulative layers 20 are removed therefrom.

The photoconductive materials and phosphors used in the above-describedphotoconductive plates and face plates will be described in more detailin examples hereinafter, but

preferable combinations of these materials are set forth in (Zn Cd=5842) (Znjie) SiO, Mn CdSe binder) All of the materials in Table I aresensitive to electron beams, ultraviolet rays, X-rays and toillumination.

So far the structures of the photoconductive plates employable in thepresent invention have been described with reference to FIGS. 1, 3a and5a through 5f. The structures of face plates adapted to be applied tothe cathode ray tubes according to the present invention have beendescribed with reference to FIGS. 6a through 6g. The results, advantagesand features of the invention are accomplished by combination of suchphotoconductive plates and cathode ray tubes having such face plates. Asdescribed hereinabove, it is imperative in the present invention that atleast a substrate, a photoconductive layer and a charge-retaininginsulative layer are maintained in the form of a lamination in the firstcharging step of charging and in the second charging step performedsimultaneously with image irradiation by electron beams in theelectrostatic image-forming process of the electrostatic recordingprocess of the present invention. This imperative condition can be metby arrangements of the photoconductive plates or face plates having theforegoing structures or by combination of photoconductive plates havingsome of the required layers and face plates having the other layers,whereby arrangements or combinations are provided to which the abovedescribed steps of the process of the present invention are applicable.

When the plates shown in FIGS. 1, 3 a, 5a and 6b which have all of therequired fundamental layers are used in forming electrostatic patterns,in the second step of the process of the present invention, theradiation image is either projected upon the photoconductive plate asshown in FIG. 7 or the photoconductive plate is disposed in closecontact with the face plate as shown in FIGS. 9 and 10 so as to directlyreceive the radiation image therefrom. In both cases, the second voltageis applied to the plate insulative layer simultaneously with emission ofthe electron beams and the electrostatic image is formed directly uponthe photoconductive plate or upon a charge-retaining recording memberinterposed between the face plate and the photoconductive plate as shownin FIG. 11.

When such recording member is used, the process includes the step ofcharging the recording member and then overlay ing same upon thephotoconductive plate or the step of charging the photoconductive plateand then overlaying the recording member thereupon.

It is to be understood that, in the processes or examples which will bedescribed hereinafter, when the recording member is overlaid upon thephotoconductive plate or upon the face plate of a cathode ray tube,either of said two steps is practiced.

The photoconductive plate shown in FIG. 5c is used in combination withone of the face plates shown in FIGS. 6a, 6b and 60 with thephotoconductive layer being maintained in contact with the face plate asshown in FIG. 18, thereby forming an electrostatic image upon insulativelayer 3.

The photoconductive plates shown in FIGS. 5d, 5e and 5f are used incombination with a conventional cathode ray tube and are maintained incontact therewith as shown in FIG. 12. Alternatively, thesephotoconductive plates may be used in the manner as shown in FIG. 8wherein the radiation image is projected thereupon. In both cases, theinsulative layer is maintained in close contact with the photoconductivelayer when the radiation image is projected thereupon and a secondvoltage is simultaneously applied thereto. These photoconductive platesmay be also utilized in combination with one of the face plates shown inFIGS. 6a, 6b and 60. In this case, a charge-retaining recording memberis interposed between the photoconductive layer of the photoconductiveplate and the face plate while the radiation image is projected and asecond voltage is simultaneously applied thereto, thereby forming anelectrostatic image upon the recording member.

The face plates shown in FIGS. 6a through 6g can be used with or withoutthe above-described photoconductive plates to form an electrostaticimage. Thus, the face plates shown in FIGS. 6a, 6b'and 60 may be used incombination with the photoconductive plates shown in FIGS. 5c, 5d, 5eand 5f or in combination with the photoconductive plates shown in FIGS.1, 3a, 5a and 5b in such an arrangement shown in FIG. 13 or 14. In thisarrangement, a high voltage is applied to the face plate as the secondvoltage while simultaneously projecting the radiation imagecorresponding to the electron beam signals, thereby forming anelectrostatic image upon the photoconductive plate, or acharge-retaining recording member is interposed between the face plateand the photoconductive plate.

The face plates shown in FIGS. 6e and 6g are adapted to formelectrostatic images upon the face plates themselves. As shown in FIG.19, electrostatic images can be formed directly or, as shown in FIG. 12,electrostatic images can be formed upon charge-retaining recordingmembers overlaid upon the face plates.

The face plates shown in FIGS. 6d and 6f are used in such a manner thatthe charge-retaining insulative layer is overlaid upon each of theseface plates when the secondary voltage is applied thereto whilesimultaneously projecting thereupon the radiation image corresponding tothe electron beam signals, thereby forming the electrostatic image uponthe insulative layer. In this case, the first charging may be appliedeither to the photoconductive layer of the face plate or to thechargeretaining insulative layer. Alternatively, the first and secondvoltages may be applied after the insulative layer has been overlaid onthe face plate.

So far the processes for forming electrostatic images by use of thecombinations of the photoconductive plates and face plates according tothe present invention have been described. But it will be understoodthat the present invention is not limited thereto and that the presentinvention covers variations and modifications made in the followingexamples and in the processes defined in the appended claims withoutdeparting from the true spirit of the present invention.

One embodiment of a process for forming an electrostatic imagecorresponding to electron beam signals according to the presentinvention will now be described with reference to FIG. 7 whichillustrates a process in which facsimile signals are converted intoradiation images which in turn are recorded as electrostatic images. Theimage provided on a cathode ray tube is projected upon photoconductiveplate A through an optical system including reflecting mirror 4a, lens5a, etc.

The facsimile or input signals are detected by detector 13a andseparated into video signals and synchronizing signals. The former areamplified by amplifier 14:: and applied to control grid 15a of a CRT forcontrolling the electron beams emitted by cathode 16a. The electronbeams are accelerated by acceleration grid 17a and focused by focusinggrid so as to produce a small electron beam cross-sectional area. Then,by deflection electrodes 1911, the beams scan phosphor screen 20a. Thesynchronizing signals are separated by synchronizing separation circuit21a into vertical and horizontal sync. signals which are in turn appliedto deflection circuits 22a and 23a respectively and finally to thedeflection coils. These synchronizing signals also control motor 24a,which rotates a drum carrying thereupon photoconductive plate A,

through control circuit 25a so as to synchronize the rotation of plate Ais completely exposed by a lamp 9a, thereby increas-v ing the contrastof the electrostatic image, whereby an electrostatic image having astrong external field and large surface potential difference is formed.

Such electrostatic image may be electrostatically transferred to copyingpaper, or as shown in FIG. 7, the image may be developed by toner inprocessor a and then transferred to copying paper 11a. Thereafter,photoconductive plate A is cleaned by cleaner 12a for repetitive use.

In this embodiment, P 11 (ZnS activated by Ag) was used as the phosphorscreen of the cathode ray tube. As the photoconductive plate A,amorphous SeTe (Te: mol was vacuum deposited upon the drum to athickness of about 40 p. and upon this SeTe layer was applied apolyester film 25 in thickness by using an adhesive of epoxy resin. Thefirst charging was made by corona discharging device 6a supplied with anegative voltage of 8 kv. so to negatively charge the polyester film toabout 2,000v. Next, simultaneously with the projection of the image, thesecond charging was made by discharging'device 8a having an opticallyopen upper end and being supplied with 7kv. Thereafter, by illuminationlamp 9a, such as a tungsten lamp, the whole surface of photoconductiveplate A was uniformly illuminated, whereby an electrostatic image havingabout 6008 was obtained.

In the above embodiment, the photoconductive plate shown in FIG. 1 wasused, but the photoconductive plate shown in FIG. 5a may also be used inthis process. It will be understood that such plate interchangeabilityis also possible in the embodiments or examples which will be describedhereinafter.

FIG. 8 illustrates one variation of the embodiment described hereinabovewith reference to FIG. 7. In this variation, transparent insulativelayer 3 of the photoconductive plate is separated therefrom and issubjected to previous first charging by device 6a. Thereafter theinsulative layer is advanced so as to be placed in close contact withthe photoconductive plate secured opposite charging means 7b. Theelectrostatic image can be formed in the manner described above and theninsulative layer 3 is removed from the photoconductive plate forprocessing or transferring of the formed image. 7

Since the photoconductive plate is made of a material having a quickresponse, the photoconductive plate 4'b may be used in stationaryposition. In this case, the scanning of the face plate by theinformation signals and the advance of the recording film 3 arecontrolled by synchronizing device 15b and motor 16b. Reference numerals4b, 5b and 8b designate respectively a mirror, a lens and a chargingdevice shield.

In FIGS. 9 and 10, another embodiment of the present invention is shownwherein a photoconductive plate of the type shown in FIGS. 1 and 5a isplaced in contact with a face plate of a cathode ray tube therebyforming an electrostatic image. Like reference numerals are used todesignate like parts in FIGS. 9 and 10.

Cathode ray tube 10 has a face plate comprising phosphor screen andglass plate 30. Photoconductive plate 40 is composed of a lamination ofinsulative layer 401, made of a material having high resistivity andresistance to abrasion such as fluoroplastics, polycarbonate resin,polyethylene resin, polyester resin or the like, photoconductive layer402 and transparent, conductive thin layer electrode 403 formed byvacuum deposition of a metal.

Photoconductive plate 4c is adapted to be placed in contact with theface plate of the CRT. For this purpose, photoconductive plate 4c is anendless belt advanced by annular frame 50 encircling the CRT as shown inFIG. 9 or by guide rollers 6c, 7c and disposed about the cathode raytube as shown in FIG. 10.

Insulative layer 4c1 of photoconductive plate 4c is first charged bycharging device 9c and then the charged photoconductive plate isadvanced toward the face plate of the CRT where phosphor screen 2c ofthe CRT is illuminated in accordance with signal information convertedinto electron beams whereby photoconductive plate 4c is exposed. At thesame time, the photoconductive plate is subjected to DC or AC coronadischarge from discharging device 10c supplied with a voltage having apolarity opposite to that of the first charge, whereby an electrostaticimage in accordance with the CRT presentation is recorded uponinsulative layer 461. Thereafter, photoconductive plate 4c is furtheradvanced and is illuminated completely by ambient light or byillumination lamp 110, thereby imparting high contrast to theelectrostatic image.

Thereafter, the electrostatic image is transferred to copying paper (SeeFIG. 10) and developed and fixed according to well-known methods ofelectrophotography. Alternatively, as shown in FIG. 9, the electrostaticimage thus-formed upon photoconductive plate 4c can be developed bytoner in processor and then transferred to copying paper 140.Thereafter, photoconductive plate 40 is cleaned by cleaner forrepetitive use.

In this embodiment, in order to synchronize the CRT presentation withthe second charging and also with the stopping of photoconductive plate40 during this second charging, both motor 190 which advancesphotoconductive plate 40 and discharging device 10c are controlledthrough sync. separation circuit 180 and the CRT is actuated by inputinformation applied through signal amplifier to deflection synchronizingcircuit 17c. High voltage source 200 and transfer bias voltage source210 are provided for the CRT. When a photoconductive material having aquick response is used, electrostatic images can be formed even if drum6c or belt 40 are moved continuously. This effect was attained by theuse of CdS.

In FIG. 11, insulative film 22c is overlaid upon photoconductive plate 4when this plate is placed upon the face plate of CRT. lnsulative film22c may be made of the same material as insulative layer 401, such asMylar (polyethylene terephthalate). Insulative film 22c is charged priorto being overlaid upon photoconductive plate 40 by charging device 9c.After formation of the electrostatic image, the insulative film isremoved from photoconductive plate 40. The use of insulative film 220much facilitates processing following image-forming, such asdevelopment, fixing, etc.

In this case, discharge occurs between insulative layer 4c] andinsulative film 220 when the film is removed from plate 4c and means forpreventing this discharge must be provided such as is shown in FIG. 12.Therein, insulative layer 401 of photoconductive plate 4c is removedtherefrom and insulative film 22 is overlaid directly uponphotoconductive layer 4c2. The whole surface of the insulative film isilluminated completely after being removed from photosensitive plate 4cso that the electrostatic image may have a strong external field andhence improved contrast. Therefore, illumination lamp 110 forilluminating the whole surface of photoconductive plate 4c is notnecessary in this embodiment.

Face plates of the type shown in FIGS. 60, 6b and 6c may be used in themanner shown in FIG. 13. That is, exterior of the glass plate of theface plate of the CRT is formed thin layer electrode 230 upon which isoverlaid photoconductive plate 40 composed of insulative layer 401,photoconductive layer 4C2 and electrically conductive substrate 403. Avoltage E is applied to electrode 23c for secondary chargingsimultaneously with the exposure. Alternative usages of insulative film220 are shown in FIGS. 14 and 15.

In FIG. 16, photoconductive plate 4c is reciprocated upon the face plateof CRT while insulative film 220 which has been previously charged isadvanced in only one direction.

When a separating agent such as silicon oil, Teflon(polytetrafluoroethylene) oil, or the like is applied between insulativefilm 22c, electrode 230 and insulative layer 4cl, their service livescan be lengthened. This application of a separating agent provided aremarkably better effect when the electrostatic image was transferredbecause the latent image was transferred through the separating agent inliquid form.

As shown in FIG. 17, when fiber optics 240, each fiber of which has adiameter of from to 25 [1,, is used as the glass plate of the face plateof the CRT in order to reduce loss due to diffraction of light passingtherethrough, resolution can be improved to about lines/mm. Formaintaining a high degree of vacuum in the envelope of the CRT, mica 250or the like may be interposed between phosphor screen 2c and the fiberoptics.

FIG. '18 shows a still further variation of the present invention. Fiberoptics 240, each fiber of which has a diameter of from 10 to p., issecured to the face plate of the CRT. At the end of optics 24c, thinlayer electrode 26c is provided by vacuum deposition of metal or thelike, and the photoconductive plate composed of a lamination ofphotoconductive layer 4c2 and insulative layer 4c1 are moved across thesurface of electrode 26. Electrode 260 is grounded and insulative layer461 is charged by charging device 9c. Upon exposure of thephotoconductive plate to the phosphor image of the CRT, thephotoconductive plate is charged with a polarity opposite to that of thefirst charging by means of second charging device 10c, thereby formingan electrostatic image upon insulative layer 4c1.

In this case, it is necessary to slide the insulative layer in closecontact with electrode 260 so that it is preferable to use a materialhaving a low coefficient of friction, such as polyester resin,fluoroplastics and so on, as the insulative layer.

Furthermore, as described above, where a separating agent such assilicon oil, Telfon oil or the like is applied between electrode 26c andphotoconductive layer 462, their service lives can be lengthened. Whenthe electrostatic image is transferred, remarkably better results areobtained because the electrostatic image is transferred through suchoil.

The use of a face plate of the type as shown in FIGS. 6e and 6g incombination with a cathode ray tube will now be described.

Referring particularly to FIG. 19, the CRT includes phosphor screen 1dadapted to be illuminated by bombardment of electron beams. Transparentelectrode layer 4d] is applied to the exterior of the CRT face plate,for example, by vacuum deposition of a metal. Photoconductive plate 4dcomposed of a lamination of photoconductive layer M2 and high resistancetransparent insulative layer 4113, made for example, of Mylar or thelike, is overlaid upon electrode layer 4d1.

insulative layer 4d3 of photoconductive plate M is charged by firstdischarging device 2d and, at the instant when photoconductive plate 4dis exposed to illumination from phosphor screen id in response toinformation signals, the photoconductive plate is discharged by DCsecondary charging, or AC corona discharge, having a polarity oppositeto that of the first charge provided by second charging device 3d,whereby an electrostatic image is formed upon insulative layer 4:13 ofphotoconductive plate 4d. Thereafter, the whole surface of thephotoconductive plate is illuminated whereby contrast of theelectrostatic image is further improved.

Then, the electrostatic image is toner-developed upon the surface ofphotoconductive plate 4d and transferred to a copying paper. The surfaceof the photoconductive plate is cleaned and the remaining charges areremoved therefrom for repetitive use. Repetitive recordings ofluminescent CRT images are thus effected.

In one method for illuminating the whole surface of the photoconductiveplate insulative layer M3 is made of a of the face plate of CRT. In analternative method, such radiation is directed uniformly upon the faceplate from inside the cathode ray tube as shown in FIG. 19 by electrongun 5d which is adapted to emit such radiation or by untraviolet raygenerating means 6d and lens 7d. Alternatively, an electron gum to whosegrid is applied a constant negative potential may be used forbombardment of the face plate with electron beams.

One example of the structure of a face plate of the type described inthe above embodiment is shown in FIG. 20. Upon one side of chromium ironframe le was fixedly attached by molten glass 9e, glass layer 2e havinga Nesa coating with Nesa film 3e being directed outwardly. Next amixture, in which CdS powder was uniformly dispersed in epoxy resin witha weight ratio of 96 4, was applied to a thickness of about 30 p. use ofa squeegee upon Nesa film 3e, thereby forming photoconductive layer 62.Polyester film 7e about 25 p. in thickness was secured to layer 6e byresin adhesive. After the resin adhesive has been sufficiently cured, amixture consisting of ZnS activated by Ag, CdS (ratio 58 42) and asynthetic resin was applied to the surface of the Nesa glass oppositethe Nesa film, thereby forming phosphor screen 4e. A coating 5e ofaluminum of about 500 A. thickness was applied to the phosphor screen byvacuum deposition, thereby providing a metal backing. Frame he of thethus-obtained face plate was secured to metallic tube 82, and thenelectron gun 5d and an ultraviolet ray emission means, e.g., hydrogendischarge lamp 6d and lens 7d in FIG. 19, were incorporated in the tube.Thereafter, the lamp was evacuated and sealed.

In FIG. 19, first charging device 2d having an optically open front end(it is not necessarily open) and second charging device 3d having alight shield plate are moved over the surface of photoconductive plate 4upon the face plate of the CRT. In practice the process of FIG. 19 takessubstantial time, thus causing slow speed operation. This defect iseliminated by the arrangement shown in FIG. 21. Over the surface ofphotoconductive plate 4f is moved a transparent or non-transparentinsulative film 5f made of the same material as insulative layer 4f3 ofphotoconductive plate 4f such as fluoroplastics, polycarbonate resin,polyethylene resin, polyester resin or the like having sufficiently highresistance to retain electrostatic charge and high resistance toabrasion. Insulative film 5f is charged before it is placed in contactwith photoconductive plate 4f. The other steps of forming electrostaticimages are similar to those described in the above embodiment. Theelectrostatic image may be recorded by either developing and fixing orby developing and transferring. Thus, this arrangement facilitates highspeed recording operations. In this case, the second charging device maybe replaced with electrode charging means. Furthermore, insulative layer4f3 may be eliminated.

When phosphor screen If of the CRT is illuminated for display of aninformation image, the second charging of photoconductive plate 4f mustbe performed. In order to synchronize these two operations, motor 10ffor driving photoconductive plate 4f and second discharging device 3fare controlled through sync. separation circuit 9f, when the informationinputs are applied to the CRT, through signal amplifier 7f anddeflection synchronization circuit 8f. Reference numeral 11f designatesa high voltage source. Furthermore, as described above, the use of fiberoptics, each fiber of which has a diameter of from 10 to 25 u, foreliminating the loss due to light scattering, provides a resolution ofabout 20 lines/mm. For maintaining a high degree of vacuum in the CRT,mica or the like may be interposed between the phosphor screen and theends of fiber optics.

The face plate of the CRT of the present invention described hereinaboveincludes at least a luminous body adapted to be illuminated uponbombardment thereof by electron beams, a transparent electrode layer, aphotoconductive layer and an insulative layer. For example, in the caseof .the face plate shown in FIGS. 19 and 21, the face plate is one of aconventional CRT and includes luminous body 1d or If illuminated uponbombardment thereof by electron beams and a tubular glass surface 3. Aphotoconductive plate on surface g comprises transparent electrode layerM1 or 4fl, photoconductive layer M2 or 4j2 and insulative layer 4d3 or 43 made of Mylar or the like. In one variation a transparent electrodelayer, a luminous body layer, a photoconductive layer and an insulativelayer may be attached to the front face plate of a cathode ray tube. Inanother variation an insulative layer is interposed between the luminousbody layer and the photoconductive layer. In a further variation aluminous body layer, fiber optics, a transparent electrode layer, aninsulative layer (this may be eliminated), a photoconductive layer, andan insulative layer may be used. In a still further variation anotherelectrostatic image-forming insulative film is used instead ofinsulative layer 4f; as shown in FIG. 21. i

We claim:

1. A process for forming an electrostatic image comprising the steps of:p

a. providing a photosensitive plate having a substrate, a

photoconductive layer overlying said substrate and an insulative layeroverlying said photoconductive layer;

b. overlaying an insulative recording member on said insulative layer;

. c. maintaining a potential of a first polarity across said plate;

and

1. while exposing said photoconductive layer to a pattern of imageradiation, 2. applying to said plate a field tending to eliminate saidfirst polarity potential, thereby forming said electrostatic image insaid insulative recording member.

2. The process claimed in claim 1 further including a terminal step ofremoving said insulative recording member from said plate insulativelayer, thereby increasing the contrast of said image formed in saidinsulative recording member.

3. The process claimed in claim 1 including the terminal step ofapplying to said photoconductive layer blanket radiation within therange of sensitivity of said photoconductive layer, thereby increasingthe contrast of said image formed in said insulative recording member.

4. The process claimed in claim 1 wherein said step of maintaining saidpotential of said first polarity across said plate is practiced byapplying charge of said first polarity to said overlying insulativerecording member.

5. The process claimed in claim 1 wherein said step of maintaining saidpotential of said first polarity across said plate is practiced byapplying charge of said first polarity to said insulative recordingmember prior to practice of said step of overlaying said insulativerecording member on said insulative layer.

6. The process claimed in claim 1 wherein said step of applying to saidplate a field tending to eliminate said first polarity potential ispracticed by applying to said plate a potential of polarity opposite tosaid first polarity.

7. The process claimed in claim 1 wherein said step of applying to saidplate a field tending to eliminate said first polarity potential ispracticed by applying alternating current corona discharge to saidplate.

8. The process claimed in claim 1 wherein said photoconductive layerexhibits P-type semiconductivity and said first polarity is negative.

9. The process claimed in claim 1 wherein said photoconductive layerexhibits N-type semiconductivity and said first polarity is positive.

10. The process claimed in claim 1 wherein said step of exposing saidphotoconductive layer to a pattern of image radiation is performed bydisposing said photosensitive plate in contact with image-formingapparatus comprising means operably res onsi ve to information signalsfor emitting electron beams efinmg said image and p ate meansll1ClUdlllg a radiation image-generating layer comprising a materialemitting radiation upon electron beam bombardment thereof and anelectrode transmissive to said radiation and overlying said radiationimage-generating layer, said image-generating layer intervening saidelectron beam emitting means and said electrode, and applyinginformation signals definitive of said image to said image-formingapparatus.

11. The process claimed in claim 1 including the further step ofvisualizing said electrostatic image on said insulative recordingmember.

12. The process claimed in claim 11 including the further step of fixingsaid visualized image on said insulative recording member.

13. The process claimed in claim 11 including the further step oftransferring said visualized image to a copying member.

14. The process claimed in claim 13 including the further step of fixingsaid transferred visualized image on said copying member.

15. The process claimed in claim 1 including the further step oftransferring said electrostatic image to a copying member.

16. The process claimed in claim 15 including the further step ofvisualizing said transferred electrostatic image on said copying member.

17. The process claimed in claim 16 including the further step of fixingsaid visualized image on said copying member.

* it i 1* UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3,653,064 I Dated March 28, 1972 I I'nv ncofls') Eiichi Inoue et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 3, line 6.4, delete v "a; -surface" and insert --of surface-e.

Column 3, line 6.7, delete' "3l and insert --3a--.

Column 11, line 37., delete "60013" and insert --600v--.

Column 14, line 7, delete "untraviolet" and insert --u'ltraviolet-.

Column 14, line 9, delete "gum" and insert --gun--.

Signed and seeled this 31st day'of- October 1972. v

(SEAL) Y Attest:

ED'WARD;M.FLETGHER, JR. ROBERT GOTTSCHALK Attestlng OfflCGIICommissionerof Patents FORM PO-105O (10-69) USCOMM-DC 60376-P69 a U754GOVERNMENY PRINTING OFFICE. I969 0365-334 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent NO. 3,653,064 Dated March 28, 1972Inventor(S) Eiichi Inoue et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 3, line 6.4, delete "a -surf ace" and insert --of surface".

Column 3, line 647, delete "'31" and insert --3a.

Column 11, line 37, delete "60015" and insert -600 Column 14, line 7,delete "unt reviolet" and' insert "ultraviolet".

Column 14, line 9, delete "gum" and insert --gun-- .Signed and sealedthis 31st day of-Cctober 1972 (SEAL) I Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting: Officer Commissionerof Patents FORM PC4050 1 USCOMM-DC 60376-P69 LLS. GOVERNMENT PRINTINGOFFICE I959 0-356334

2. applying to said plate a field tending to eliminate said firstpolarity potential, thereby forming said electrostatic image in saidinsulative recording member.
 2. The process claimed in claim 1 furtherincluding a terminal step of removing said insulative recording memberfrom said plate insulative layer, thereby increasing the contrast ofsaid image formed in said insulative recording member.
 3. The processclaimed in claim 1 including the terminal step of applying to saidphotoconductive layer blanket radiation within the range of sensitivityof said photoconductive layer, thereby increasing the contrast of saidimage formed in said insulative recording member.
 4. The process claimedin claim 1 wherein said step of maintaining said potential of said firstpolarity across said plate is practiced by applying charge of said firstpolarity to said overlying insulative recording member.
 5. The processclaimed in claim 1 wherein said step of maintaining said potential ofsaid first polarity across said plate is practiced by applying charge ofsaid first polarity to said insulative recording member prior topractice of said step of overlaying said insulative recording member onsaid insulative layer.
 6. The process claimed in claim 1 wherein saidstep of applying to said plate a field tending to eliminate said firstpolarity potential is practiced by applying to said plate a potential ofpolarity opposite to said first polarity.
 7. The process claimed inclaim 1 wherein said step of applying to said plate a field tending toeliminate said first polarity potential is practiced by applyingalternating current corona discharge to said plate.
 8. The processclaimed in claim 1 wherein said photoconductive layer exhibits P-typesemiconductivity and said first polarity is negative.
 9. The processclaimed in claim 1 wherein said photoconductive layer exhibits N-typesemiconductivity and said first polarity is positive.
 10. The processclaimed in claim 1 wherein said step of exposing said photoconductivelayer to a pattern of image radiation is performed by disposing saidphotosensitive plate in contact with image-forming apparatus comprisingmeans operably responsive to information signals for emitting electronbeams defining said image and plate means including a radiationimage-generating layer comprising a material emitting radiation uponelectron beam bombardment thereof and an electrode transmissive to saidradiation and overlying said radiation image-generating layer, saidimage-generating layer intervening said electron beam emitting means andsaid electrode, and applying information signals definitive of saidimage to said image-forming apparatus.
 11. The process claimed in claim1 including the further step of visualizing said electrostatic image onsaid insulative recording member.
 12. The process claimed in claim 11including the further step of fixing said visualized image on saidinsulative recording member.
 13. The process claimed in claim 11including the further step of transferring said visualized image to acopying member.
 14. The process claimed in claim 13 including thefurther step of fixing said transferred visualized image on said copyingmember.
 15. The process claimed in claim 1 including the further step oftransferring said electrostatic image to a copying member.
 16. Theprocess claimed in claim 15 including the further step of visualizingsaid transferred electrostatic image on said copying member.
 17. Theprocess claimed in claim 16 including the further step of fixing saidvisualized image on said copying member.